Vehicle headlight



Jan. 13, 1931. w. H. WOOD 1,788,937

VEHI GLE HEADLI GHT Filed Nov. 5, 1927 I 199 F1910 8 /5 A j: VzZZ'Izhm H Wave? 8 Ipverz tax- Attorneys Patented Jan. 13, 1931 UNITED STATES WILLIAM H. WOOD, 01B SOUTH EUCLID, OHIO VEHICLE rimmenr Application filed November 3, 1927. serial No. 230,718.

This invention relates to vehicle headlights and has for its object the provision of a new and improved lens which shall facilitate the use of a two filament lamp. The

two filament lamp which I particularly con-- template is one havin two independently usable light sources concentrated form, located one substantially above the' other, the purpose of the same being to enable the driver to elevate his light beam to the most "advantageous angle when driving on a deserted road .or to depress the same when meeting other travelers. The filaments of such lamps'are generally. made of concentrated shape, that is to say of very fine wire coiled into small compass, each coil often consisting of a small helix bent to a V-shape with its plane horizontal and its apex presented forwardly, andsuch is the nature of 2 the device Ihave illustrated in connection with this application, although I do not limit myself thereto.

When any such lamp bulb is employed in connection wit a paraboloid reflector the lamp is ordinarily located with the filaments in the same vertical line which contains the focal point of said paraboloid, one being above the parabolic axis and the other at or below such axis. However, shifting from one light source to" the otherin such areflector tends to cause a certain separation of the reflected rays accompanied by a more or less complete reversal of light pattern. The object of the present invention is the provision of a simple and inexpensive type of lens which shall overcome the tendency of the reflected rays to split into a series of vertically spaced rings or bands and instead.

thereof a smooth and unbroken horizontal light pattern may be obtained which shall merely be depressed a few degrees upon shifting from the lower filament to the upper filament, without substantial change in shape or intensity and independent of a considerable variation in the position of said incandescent light source inside said reflector,

either axially .or 'vertically. With this essential feature of my, nvention other expedients can be employed to spread the light laterally,

these last consisting either of a fiatting or fluting of the reflector or a vertical ribbing of the lens a's-may be desired. It is important, however, to the successful use of such a device that the light pattern should show a minimum of horizontal bands or striae since such appearance is always accentuated by any departure of the filaments from their accurate focal position.

In the drawings accompanying and forming a part of this application I have shown certain illustrative embodiments of my in-' vention together with certain diagrammatic views illustrating the principles thereof. Fig. 1 is a vertical axial view through a vertically ribbed reflector, sometimes known as 5 the flat-lite type of reflector, equi ped with my improvements; Fig. 2 is a horizontal sectional view corresponding to the .line 2-2 of Fig. 1; Fig. 3 is a front elevation of the lens shown in Fig. 1; Fig. 4 is a vertical axial section through a plain paraboloid type of headlight equipped with another form-of my improvedlens; Fig. 5 is a horizontal sectional view on the line 5-5 of Fig. 4; Fig. 6 is a front elevation of the lens shown in Fig. 4; and Figs. 7 to 10 inclusive are diagrammatic views showingthe preferred relation of curvatures of the different prisms.

I have shown merely the essentials 0% a so headlight, namely, reflector 1,-socket 2, lamp bulb 3 and lens 4. The reflector ,in Figs. 1 and 2 is formed with vertical zones 5-5 of modified transverse curvature while the reflector 1 shown in Fig. 4 is unstriated. The lamp bulb is formed with two filaments 6 and 7 locatedone above the. other substantially in the same vertical line which con tains the focal point of the reflector and. i

with the lower filament s at or slightly be-' low the reflector axis, the filament 7 being located above such axis. -The, lens 4 shown in Figs. 1 and 3 is formed in a central hori= zontal zone whose end portions 9-9 are free from prisms. while above that zone are lo-v cated a plurality of parallel, level, prismatic ribs at 10, 11, 12, 13,14, increasing progressively'in slope with increasing distance from said zone; while below said zone are other parallel, level, prismatic ribs 15, 16, 17, 18, 19, also slanted in the same direction as the first named ribs and also increasing progres- 'sively in slope with increase of distance from said central zone. Thus far the construction is the same as that described and claimed in my application filed June 30, 1926, Serial No. 119,557. I have found, however, that it is very desirable that the inclined surfaces of these ribs be curved instead of straight so as to produce a better diffusion of the light and prevent the occur-' rence of anyhorizontal bands or striations in the light field; furthermore it is desirable that this curvature should be in the opposite sense in the upper and lower halvesof the lens, being convex above and concave below; and finally it is desirable that uniformity of curvature be secured by causing these 'ribs to conform to different portions of the outline of one and the same conic section; these features have independent value, although I have chosen for illustrative purposes a lens which combines all those features in one structure.

The advantage of basing all the prisms upon a single known curve is that the amount of the lens effect can be calculated accurately in advance. It is known, for ex-.

ample that the effect of the upper filament is to elevate above the axis those rays which are reflected from that part of the reflector which lies at and near the axial vertical plane and in front of the focal plane, the elevation increasing with increasing distance from the focal plane. Hence a gradually increasing refraction is necessary not only to compensate for this elevation but also to depress therays well below the horizontal to produce a near light, yet without over depressing the rays which are reflected at or near the focal plane.

This graduated refraction is produced by the use of a lens having the curvature of its face portion (as measured along a vertical axial section) conforming to a segment of a conic section, the curvature being a minimum adjacent the central horizontal zone and increasing both upwardly and downwardly from that zone. Said zone is left to permit the passage of the distance beam. The conic section adopted may be a circle, ellipse, parabola,'or hyperbola, and such a slope of said curve must be chosen next the reflector as shall depress the beams of maximum tendency to diverge, regard being had to the coeflicient of refraction of the glass used.

Thus in Fig. 7 I have taken a segment 20 of a circle containing between its extremities the maximum and minimum slope desired, and cause the ribs 10, 11, 12, 13, 14 to conform thereto, thereby securing a uniformly graded deflection of the light. through the different portions of the lens as is necessary to compensate for the gradually increasing tendency towards aberration experienced as one approaches the upper margin of the reflector. Similarly I may take another circle 21 (which may be the reverse of the same circle) and cause the ribs 15, 16, 17, 18 and 19 to conform to different sections thereof in a concave sense as shown in Figs. 9 and 10. The optical effect produced by a series of segments having flat reverse faces and curved prismatic faces is the same regardless of the depth of those sections, so that the optical effect of the lenses illustrated in Figs.8 and 19 is the same as that which would be produced by lenses of the cross section shown in Figs. 7 and 9 respectively, since theshaded portions thereofcan be omitted without optical effect owing to the fact that their opposite sides are parallel.

In the form of the invention shown in Fig. 1 I have shown one facebf the lens as plane owing to the lateral spreading effect of the striations Inthe absence of those strations as shown in Fig. 4, or to increase the lateral dispersion for any other reason, I may form the face of the lens opposite the prisms heretofore described with vertical flutes or ribs 25, although when-the same are .used they are preferably omitted from the lateral portions of the central zone 9-9, so

as to permit the distance beam to issue unmodified from this portion of the reflector. The middle portion of this zone may be handled in any suitable or desired manner. In the present embodiment I have shown this portion as having a slightly convex face 26 along its upper margin mergin gradually with a slightly concave face 2 along its lower margin the two being connected by a more or less extensive fiat portion along the center line.

As a result of the. constructions herein described the rays reflected from the upper and lower regions of .the reflcctor are defiected downwardly,-not uniformly. nor by' discrete increments, but in a gradually varying amount, the deflection being greatest where the tendency to produce glare from the upper filament is greatest. It is also found that upon a shift from one filament to the other the distance beam is raised or lowered by a small angle while the near light, which issues from the portions of the reflector at and near the vertical axial plane, is merely caused to shift-in the same direction as the distance beam but by a smaller amount, the pattern remaining much' the same. Owing to the curvature of the ribs and the graduated slope thereof the light field is uniformly illuminated and accurate individual positioning of the light bulb in the reflector is unnecessary. since the tolerance limits become sufiiciently wide to cover the usual manufacturing variations.

areaeev center being concave and the deflecting efiect increasing in each direction toward the upper and lower margins 2. A lens for the purpose described having on one face a plurality of level prismatic ribs all sloped in one direction, the degree of slope gradually decreasing from without inwardly, and the .faces of said ribs being rounded, those above the center being convex and those below the center being concave.

3. A lens for the purpose described having on one face a lurality of adjacent straight parallel ribs tl ie faces of which all slope in one direction and are curved in vertical section so as tov conform to adgacent portions of one and the same curve line.

4. A lensfor the purpose described having on one face a plurality of adjacent straight parallel ribs the faces of which all slope in" one direction and are curved in vertical section so as to conform to adjacent portions of one and the same conic section, the portions of least slope being located nearest the central zone of the lens.

5. A lens for the purpose described having on one side of its center aseries of parallel ribs, and on the opposite side of its center a' second series of parallel ribs, the faces of adjacent ribs in each series conforming to adjacent portions of a conic section, the faces of the ribs in the one series being convex and those in the other series concave.

6. A lens for the purpose described having on one side of its center a series of parallel ribs, and on the opposite side ofits center a second series of parallel ribs, the faces of adjacent ribs in each series conforming to adjacent portions. of a conic section, the faces of the ribs in the one series being convex and those in the other series concave, and the slo e of the ribs increasing with increase of t e distance from the lens center.

7. A lens for the purpose described having at one side of its'central zone a series of parallel ribs and on the o posite side-of its central zone a second series of parallel ribs, all of said ribs sloping in the same direction and the slope of the ribs increasing with increase of the distance from the lens center in each direction, the faces'of the ribs being rounded.

8. A lens for the purpose described having at one .side of its central zone a series of parallel ribs and on the opposite side of its central zone a second series of parallel ribs, all of said ribs slopin in the same direction and the slope of the llbS increasing with increase of the distance from the lens center in each direction, and the faces of the ribs being concave on those ribs whose faces slant inwardly and convex on those ribs whose faces slant outwardly.

i In testimony whereof-It hereunto afix my signature. 4

WILLIAM H. WQOD 

